1. Field of the Invention
The present invention relates to an image forming apparatus, and more particularly, to a configuration in which a regulation portion configured to regulate a position of a sheet contained in a sheet feeding cassette is held at a regulation position.
2. Description of the Related Art
There is widely used an image forming apparatus, such as a conventional copier, printer, or facsimile, in which a sheet feeding device is provided and a sheet is fed from the sheet feeding device to an image forming portion to thereby form an image. In such a sheet feeding device, in general, a sheet feeding cassette serving as a sheet containing portion is removably mounted to an image forming apparatus main body, and a sheet contained in the sheet feeding cassette is automatically fed to the image forming portion by a sheet feeding roller.
A cassette body of the sheet feeding cassette containing the sheet is provided with a trailing edge regulation portion configured to regulate a position of an upstream edge (hereinafter, referred to as a trailing edge) in a sheet feeding direction of the contained sheet. Further, the cassette body is provided with side edge regulation portions configured to regulate side edge positions of the sheet in a direction (hereinafter, referred to as a width direction) orthogonal to the sheet feeding direction.
When the sheet is contained in the sheet feeding cassette, the side edge regulation portions regulate the side edge positions of the sheet, whereas the trailing edge regulation portion regulates the trailing edge of the sheet. Accordingly, a leading edge position of the sheet is always regulated to be located at a predetermined position at which sheet feeding is possible. With this configuration, when the sheet feeding cassette is mounted to the image forming apparatus main body, it is possible to perform stable sheet feeding regardless of a sheet size.
Incidentally, in such a sheet feeding cassette, there is widely known a sheet feeding cassette in which the trailing edge regulation portion and the side edge regulation portions are slidably provided to the cassette body in order to easily perform switching of a position of the trailing edge regulation portion and positions of the side edge regulation portions according to the sheet size. In the sheet feeding cassette having the above-mentioned configuration, in order to set and hold the position of the trailing edge regulation portion and the positions of the side edge regulation portions, the trailing edge regulation portion, the side edge regulation portions, and the cassette body are provided with rack claws or engagement teeth formed at a constant fine pitch. By engaging the rack claws of the trailing edge regulation portion and the rack claws of the side edge regulation portions with the rack claws of the cassette body, the position of the trailing edge regulation portion and the positions of the side edge regulation portions are determined. By releasing engagement between the rack claws, changing of the positions of the regulation portions (switching of the sheet size) is possible. The above-mentioned configuration is disclosed in Japanese Patent Application Laid-Open No. H08-217262.
However, in the image forming apparatus and the sheet feeding device provided with the above-mentioned conventional sheet feeding cassette, there is a problem in that the position of the trailing edge regulation portion and the positions of the side edge regulation portions are misaligned (moved out of alignment with proper positions) due to an impact applied when the sheet feeding cassette is inserted into the apparatus main body. When the positions of the side edge regulation portions are misaligned, the position of the sheet is misaligned, and thus right and left margins are different in width upon image formation, with the result that image quality is deteriorated. Further, when the position of the trailing edge regulation portion is misaligned, a proper positional relation is not established between the leading edge of the sheet and the sheet feeding roller, and thus sheet feeding failure such as a sheet jam or a miss feed occurs.